Computer-aided laser-based measurement system

ABSTRACT

A system having laser source and radiation sensor assemblies electrically communicating with a computer is provided for rapid, remote sensing of the static, geometric and dynamic motion properties of a selected specimen. A laser beam incrementally scans the surface of a specimen to be evaluated in response to computer generated programmed signals and the radiation sensor follows the laser beam illumination as at the specimen surface. Both the source and sensor provide output signals representing the angular position of pointing of the source and sensor assemblies. The source and sensor angle signals are triangulated in the computer for calculation of desired geometric and dynamic specimen properties. The computer can be programmed to generate a display for presentation of the specimen properties or for governing industrial control, inspection or processing systems, that are related to the specimen properties measured.

stated tates tet [72] Inventor Oleg Svetlichny Chelmsiord,.

[2]] Appl. No. 34,197

[22] Filed May 4, 1970 [45] Patented Jan. 4, 1972 [73] AssigneeGeosystems, Inc.

Burllngton,Mess.

[54] COMPUTER-AIDED LASER-BASED MEASUREMENT SYSTEM 9 Claims, 10 DrawingFigs.

52] U.S.Cl 255/1515, 33/46 R, 33/125 A, l48/9.5,235/l51.l, 356/1, 356/4,356/152 OTHER REFERENCES Lamy, R. C. et al. Computer Controlled GrinderOperation in IBM Tech. Disc. Bull. 12(12): May 1970 P. 2,156

Primary Examiner-Malcolm A. Morrison Assistant Examiner-R. StephenDildine, Jr. Attorney-Morse, Altman 8L Oates ABSTRACT: A system havinglaser source and radiation sensor assemblies electrically communicatingwith a computer is provided for rapid, remote sensing of the static,geometric and dynamic motion properties of a selected specimen. A laserbeam incrementally scans the surface of a specimen to be evaluated inresponse to computer generated programmed signals and the radiationsensor follows the laser beam illumination as at the specimen surface.Both the source and sensor provide output signals representing theangular position of pointing of the source and sensor assemblies. Thesource and sensor angle signals are triangulated in the computer forcalculation of desired geometric and dynamic specimen properties. Thecomputer can be programmed to generate a display for presentation of thespecimen properties or for governing industrial control, inspection orprocessing systems, that are related to the specimen propertiesmeasured.

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INVENTOR OLEG SVETLICHNY STABLE BASE BY FIG. 4

ATTORNEYS PATENTEUJAN 41972 3,833,010

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F 7 b ATTORNEYS COMPUTER-AIDED LASER-BASED MEASUREMENT SYSTEM BACKGROUNDOF THE INVENTION 1. Field of Invention The present invention relates tosensing systems and, more particularly, to rapid remote sensing ofstatic, geometric and dynamic motion properties.

2. Description of the Prior Art Sensing instruments of various typeshave been proposed for determining static, geometric and dynamicproperties of a specimen, such as surface contour, resonant frequency,deformation and the like. Difficulties have been encountered inevaluating subjects due to environmental conditions, complex surfacecontours, hazardous physical state, and the need to evaluate datarapidly and in real-time. A typical example of one such difficulty isevident in the steel industry where the specimen to be evaluated is asteel slab emerging from a continuous casting machine. The geometric anddynamic properties of the cast steel must be ascertained in order tocontrol he casting and working processes. Conventionally, in thecontinuous casting operation, a molten steel slab having a frozen outershell is cooled from outside by water sprays as it is guided through aseries of supporting rolls. At low casting speeds, the skin is strongand easily withstands the ferrostatic pressure of the molten steel inthe molten core However, at higher casting speeds, the skin strength isdecreased due to the thinness of and high temperature of the outershell. In consequence, the frozen skin can not withstand the ferrostaticpressure and the frozen skin bulges as the slab passes between adjacentsupporting rolls. If this bulging is excessive, a failure of the frozenskin, commonly called breakout, may occur with a potentially disastrousresult. In order to avoid such breakouts, a conservatively low castingspeed is used.

Another typical example of such difiiculty, in connection with thecontinuous casting of steel, is the on-line detection and selectiveremoval of surface defects. Presently, such defects are removed eithermanually (machining, grinding, chiseling, burning) after the slabs havebeen cooled to room temperature, or by total flame scarfing in which alayer on each of the four sides of the steel slab surface is removedduring casting. Such methods result in a high labor cost, due to themanual handling of steel slab, in the manual scarfing procedure or in asubstantial loss of yield in the total flame scarfing technique.

SUMMARY THE INVENTION An object of the present invention is to provide arapid remote-sensing measurement system which is characterized byuniversally mounted laser and radiation sensor assemblies electricallycommunicating with a computer. The surface of a specimen to be evaluatedis scanned incrementally by the beam of energy produced by the laserassembly in response to program signals generated by the computer. Theradiation sensor follows the illuminated scanned points on the surfaceof the specimen. The output signals from the laser and radiation sensorassemblies, representing angular position, are entered into the computerfor determination of the surface contour by triangulation. Thecombination of laser and radiation sensor assemblies and computer issuch as to provide a versatile and expedicious rapid, remote-sensingmeasurement system.

The invention accordingly comprises the system possessing theconstruction, combination of elements, and arrangement of parts that areexemplified in the following detailed descriptions, the scope of whichwill be indicated in the appended claims.

BRIEF DESCRIPTION OF DRAWINGS For a fuller understanding of the natureand objects of the present invention, reference should be had to thefollowing detailed description taken in connection with the accompanyingdrawings wherein:

FIG. 1 is a trigonometric diagram illustrating certain principles ofthepresent invention;

FIG. 2 is a block diagram, somewhat perspective, of a sensing systemembodying the present invention,

FIG. 3 is a schematic diagram of an alternative embodiment of FIG. 2;

FIG. 4 is a trigonometric diagram illustrating an application of thesystem to a contouring problem;

FIG. 5 is a trigonometric diagram illustrating an application of thesystem to a vibrational testing problem;

FIG. 6 is an illustration of a system embodying the present inventionfor controlling continuous casting of steel using solidified skinbulging infonnation;

FIG. 6A is a top elevation showing certain portions of FIG. 6 in detail;and

FIG. 7a-7c are a series of illustrations of a selective scarfing systemembodying the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The system operates onthe triangulation principle depicted in FIG. 1, which is based on thefact that light travels in a straight line. By measuring the anglebetween two line of sights to a common target point and knowing thelength of the base, it is possible to compute the distance to the targetpoint. The system used the high intensity, monochromaticity, and smalldivergence properties of a laser beam to define the common target point,the laser beam defining a small spot of light on the sample beingmeasured or examined. The high intensity of the laser beam makes theluminance of the spot more intense than the ambient luminance of thesample, even when the sample is a glowing steel slab. Hence, a trackingdevice mounted on the same base as the laser can easily follow thecenter of the spot without significant interference from other light.The pointing angles of the laser and the optical axis of the tracker aremeasured continuously by angular encoders. Since the baseline distanceis fixed and known, the location of the illuminated spot is established.The target distance h is computed from the following equation where:

B is a precisely known baseline length, and

0,, 0 are accurately measured by electronic devices.

Generally, the measurement system of FIG. 2 is comprised of anillumination source 10 for generating an imaged beam of energy likeradiation sensors 12, I4 for detecting illumination as at the surface ofa specimen 16; a computer 18 electrically communicating with source 10and radiation sensors 12, 14 for determining the properties of specimenl6; and a display 20 electrically connected to computer 18 forpresenting the specimen properties.

Illumination source 10 is comprised off a coherent energy generator 22pivotally mounted to a support 24 which is rotatably mounted to acontrol 26 via a housing 28. In this embodiment, light generator 22 is alaser of the type having a gasfilled tube 30, Fabry-Perot plates 32, 34fixed at opposite extermities of tube 30, and a pump 36 coupled to thegas in tube 30. Pumping power is applied to laser 22 from a supply 40via pump 36 and a coherent energy beam is emitted at 38. Various typesof coherent energy sources may be used in alternative embodiments.Control 26 includes a servo 42 for governing the pivoting movement oflaser 22 about a shaft 44 and the rotating movement of housing 28, and aservo follower 46 operatively connected to servo 42 for providing outputsignals representing the angular position of laser 22.

Each of like radiation sensors I2, 14 is comprised of aradiation-detector 48, pivotally mounted to a support 50 which isrotatably mounted to a control 52 via a housing 54, for generating errorsignals whose magnitude is representative of the radiation sensorassembly angular pointing errors with respect to the illuminated spot onthe surface of specimen 16. In order to eliminate undesired luminancefrom the surface of specimen 16, a filter S6 is placed in front ofradiation-detector 48. A signal separator 58 is electrically connectedto radiation-detector 48 for isolating the output error signals for eachof two angular coordinates. A servo 60, responsive to the signals as atthe output of signal separator 58, is connected to support 50 andhousing 54 for governing the pivoting movement of radiation-detector 48about a shaft 62 and the rotating movement of housing 54. The signals asat the output of separator 58 are such that radiation-detector 48 isdirected toward the highest intensity of luminance as at the surface ofspecimen 16. A servo follower 64 is operatively connected to servo 60,the signals as at the output of a servo follower 64 representing theangular position of radiation-detector 48. It is to be understood thatthe scope of the invention is intended to include radiation-detectorsand scanning devices such as an image dissector, a photocell, athermocouple, an array of silicon detectors, etc.

Computer 18 is comprised of an input-output 66, a central processor 68including an arithmetic unit 70, electrically communicating withinpuboutput 66, and a memory 72 electrically communicating with centralprocessor 68. Data signals as at the output of central processor 68 aretransmitted via input-output 66 for controlling illumination source 10,receiver 12 and 14, and supply 40. Angular position signals as at theoutput of servo followers 46 and 64 are applied to central processor 68via input-output 66 for calculation of the properties of specimen 16being evaluated. Specimen property signals as at the output of centralprocessor 68 are applied to display 20 via input-output 66 forpresentation. Control signals, calculated from specimen propertiesaccording to programmed instructions, are transmitted via input-output66 to external controller 75 for governing inspection, testing,manufacturing or other industrial processes in accordance with a latestmeasurement of specimen 16.

As shown in FIG. 2, specimen 16 may be mounted on a shaker 76 which isadapted for triaxial movement in response to select signals as at theoutput of driver 74. In one example of system operation, control signalsas at the output of inputoutput 66 are applied to servo 42 and supply40, in con sequence a laser beam is directed toward a selected surfacespot 78 of specimen 16. The illuminated spot as at 78 is sensed indetector 48. The signals as at the output of detector 48 are applied toservo 60 via signal separator 58, whereby detector 48 is directed towardthe illuminated spot 78 lines 80 and 82 denoting the angular position oflaser 22 and detector 48, respectively. The signals as at the output ofservo followers 46 and 64, representing angular positions 82 and 80,respectively, are applied to computer 18 via input-output 66. Thedistance between detector 48 and spot 78, is calculated by triangulationin computer 18, the distance between receiver 12 and illumination sourcebeing known. Thereafter, a second control signal is applied to servo 42,in consequence the laser beam is directed toward a selected surface spot84 of specimen 16. Detector 48 is directed toward the illuminated spotas at 84 in the manner hereinbefore described. The new angular positionsof laser 22 and detector 48 are denoted by lines 86 and 88,respectively. The new signals as at the output of servo followers 46 and64, representing angular positions 88 and 86 respectively, are appliedto computer 18 via inputoutput 66 and a new set of distance calculated.It will be readily appreciated that by incrementally scanning thesurface of subject 16 with the laser beam, the contour 6 the surface ofspecimen 16 can be obtained. Data signals representing the results ofthe triangulation calculations are applied to display 20 forpresentation. It is to be understood that in alternative embodiments thenumber of radiation sensors is other than two, for example one or three.

In a second example, shaker 76 is vibrated in response to the signals atthe output of driver 74 and laser 22 is held stationary. Accordingly, asspecimen 16 is vibrated, detector 48 follows the relative movement ofthe illuminated spot on the surface of specimen 16. The varying angularposition of detector 48 is transmitted to computer 18 via servo follower64 for calculation of the displacement, velocity and/or accelerationul'spccimcn l6.

In the alternative embodiment of FIG. 3, the radiation sensor is animage dissector tube 200 which is comprised of a photocathode 202, anelectron-optic imaging system 204, an aperture plate 206, aphotomultiplier structure 208 and an anode 210. The spot from laser 10is imaged by a lens 215 onto photocathode 202 and the photocathodeelectrons are imaged onto plate 206. Since plate 206 has a small openingor hole 212, only those electrons from a very small spot on photocathode202 enter photomultiplier structure 208. A varying voltage is applied tohorizontal and vertical deflection plates 214, 216, respectively, inconsequence the small hole is, in effect, moved around the photocathodearea. If the hole is moving in a path concentric with the spot, thesignal as at anode 218 of tube 200 is at a constant level. If the holeis moving in a path eccentric with the spot, the signal as at the anodeof tube 200 is sinusoidal. For small deviations, the magnitude of thesignal as at the output of tube 200 is proportional to the distancebetween the centers of the spot and hole path and the phase of thesignal is proportional to the direction of the error signal. Thus, ifthe DC component of the varying voltages on plates 214, 216 isreadjusted in accordance with the signal, so that the signal level isbrought close to zero, the light spot is being tracked on the tube. TheDC voltages are thus proportional to the light displacement andrepresent the desired measurement.

FIG. 4 illustrates an application of the system to a contouring problemin which the laser beam is made to scan a fixed surface. As the scanningproceeds from position A to B to C in a continuous manner, the contourof the object is generated by computing distances from the baseline ofpoints A, B, C and all points in between. Again, by feeding the outputsignals into a computer, online inspection of surfaces becomes possible.For example, closed loop control of continuous casting of steel andonline scarfing of continuously cast steel slabs, later described, arebased on the real-time contouring application of the system.

FIG. 5 illustrates an application of the system to a vibrational testingproblem. As specimen 16 moves (vibrates) from position D to D; radiationsensor 12 generates signals representing the incremental angle throughwhich its line of sight has moved in following the illuminated spot. Thesuccessive measurements provide data to compute displacement, velocity,and acceleration of specimen 16 as follows:

Displacement= AP= B (tan 0 tan 6,)

Velocity =d (AP)/dt Acceleration d (AP)/dt These computations can beperformed in real-time, when desired, by feeding the measurement data toan online computer. In an alternative embodiment of the presentinvention the number of illumination sources is other than one, forexample two. When two or more lasers are employed, the relative motionof two or more spots can be detected, hence deformation under test canbe measured. It is possible also to measure deformation using a singlebeam which alternates between two positions and scans more rapidly thanthe motion of acceleration.

In an alternative high-speed embodiment of the present invention,radiation sensor units 12 and 14 are replaced by image dissector tubesof the type shown in FIG. 3, the image of the spots 78 and 84 beingoptically focused onto the sensitive photocathode of the image dissectorin the usual manner. In this embodiment, the position of the spot imageis detected by the electrical scanning of the image dissector tube incontrast to the mechanical scanning described in connection with FIG. 2.Electrical position signals from the image dissector tubes are appliedto the computer 18 via input-output 66 and the distance between theilluminated spot and the detector are calculated by triangulation. Inthis embodiment, surface contours may be measured by scanning the lasersource 22 over the entire specimen surface 16.

In yet another alternative embodiment, the image dissector is replacedwith a silicon cell sensitive to image spot displacement in twodimensions. The electrical outputs represent image displacement and areapplied to computer 18 via inputoutput 66.

It will be appreciated from the foregoing that the system provides thefollowing key features:

1 Automated measurementsfeature is valuable for applications whichrequire many measurements in a short time and in a repetitive manner.For example, vibrational testing at 60 c.p.s. requires about 600measurements per second in order to resolve 1 percent of thedisplacement. Coupling of the output signals to an online computerallows reduction of the measurement data immediately, or the data can bepreprocessed (edited, formated, scaled, smoothed, etc.) and recorded forlater reduction. In either case, the data acquisition and reduction isautomated for efficiency and economy.

2. Remote measurementsbecause the measurements are made remotely, theapplications of the system extend into areas where the environment ishazardous to human beings and ordinary instruments. Typical examplesinclude measuring the level of molten metal, the shape of white hotsteel slabs, and measurements in the vacuum of space, in corrosiveatmospheres, explosive environments, or at high voltage.

3. Rapid measurements-the ability to track or scan rapidly permitsinspection under dynamic rather than static conditions. For example,turbine blades could be examined under conditions of full speedrotation.

4. Precision measurements-the unique properties of the laser beam andthe high resolution of angle encoders allows one to make measurements ofhigh accuracy. For example, deformations as small as one wavelength canbe detected.

5. Real-time measurements informationbecause the measurement data can befed into an online computer, the information can be used in real-time.For example, in a closed process control loop.

The following example further illustrate the application of the presentinvention. The performance of the system is determined primarily by thewavelength of light used. Typical data is as follows:

EXAMPLE I Accelerometer Applications. When the system is used to measurethe motion of an object undergoing vibrational testing, the followingapplies, using a typical laser source for viewing a small opticalquality reflecting region at the surface of the vibrating specimen:

Apparatus Parameters Wavelength of Source Illumination 0.6 micronDistance to Object centimeters Source Optical Aperture 5 millimeters 30hertz Shaker Frequency Performance Minimum Resolvable Motion 2X10 meterMinimum Detectable Acceleration 0.002 g. Frequency Response DC to beyondI MHz. Maximum Detectable Acceleration Unlimited EXAMPLE I] SurfaceContouring and Inspection Applications. When the system is used todetermine or inspect the curvature or form or shape of surfaces thefollowing applies:

Apparatus Parameters Minimum Resolution (wavelength limited) Min'imumResolution (size limited) Inspection Rate (mechanically limited)Inspection Rate (at l cm. resolution) Object size X10" meter l6 secondsper object 16 second per object Referring now to FIG. 6, there is shownone type of system embodying the present invention for control ofcontinuous casting of steel using solidified skin bulging information.Generally, the system comprises a tunduish formed with a discharge spout92; a mold 94 formed with opening 96 at one end and a discharge opening98 at the other end, opening 96 being in register with spout 92; aplurality of rolls 100, 102, 104, 106, 110, 112, 114, 116 118 and 120defining a curving path to carry a cast steel strand 122 from verticalto horizontal, rolls 100, 102, 104, 106, 108 and 110 being guide andsupport rolls, rolls 112, 114 and 116 being bending rolls and rolls 118and 120 being straightening rolls; spray nozzles 124, 126 and 128, 130disposed between rolls 104, 108 and 106, 110, respectively, and directedtoward strand 122; a pinch rolls drive 132 operatively disposed aboutstrand 122; optical conduit 136 in register with strand 122; a source148 mounted to conduit 136 for generating a beam of coherent light 150toward strand 122; a sensor 134 mounted to conduit 136 for detecting theilluminance of beam 150 as at the surface of strand 122; an air ornitrogen supply 138 operatively connected to conduit 136 via a duct 140;a computer 154 electrically connected to sensor 134 for determining thecontour of strand 122 by triangulation; a control 142 electricallycommunicating with pinch rolls drive 132 and computer 154; a spraycontrol 44 electrically connected to control 142 and each of the spraynozzles and a display 146 electrically connected to computer 154.

In operation, molten steel 156 as in tundish 90 is fed into mold 94 viadischarge spout 92 and opening 96. Mold 94 is oscillated by a drive 158operatively connected thereto so that steel 156 does not adhere therein.The surface contour of strand 22 is monitored continuously by sensor134, i.e., laser beam illuminates a spot on the surface of strand 122and sensor 134 detects the relative movement of the illuminated spot.Angular position signals representing the sequence of operations of thelaser transmitted beam and the sensor received beam are applied tocomputer 154 for calculation of the surface contour of strand 122. Inorder to maintain a steam free atmosphere in conduit 136 so that theoptical path is unobscured, compressed air or nitrogen from supply 138is blown through the conduits via duct 140. Contour signals as at theoutput of computer 154 are applied to display 146 for presentation andthe signals as at output 154 are applied to control 142 for governingpinch roll drive 132 and control 144. Spray nozzle signals as at theoutput of control 142 are applied to control 144 for controlling spraynozzles 124, 126, 128, and 130 which emit water for controlling thetemperature gradient along strand 122.

In addition to providing output signals to control 142 and display 146,computer 154 generates output signals for con trolling the castingspeed, i.e., the velocity at which strand 122 is advanced along the path(which is shown as being curved but which may be linear) by pinch rolls160 and 162. As previously stated, the amount of bulge, as shown in FIG.at 249, is dependent on the ferrostatic pressure within the molten core,the thickness of the frozen skin, and the temperature gradient withinthe frozen skin. The optimum casting speed is computed on the basis ofthe measured bulging of the skin at 249 and the characteristics of thesteel.

In an alternative embodiment, laser and receiver assemblies are providedon opposite sides of strand 122, for eliminating errors caused by motionof the rolls and mold.

FIG. 7 is a schematic of a selective scarfing system embodying thepresent invention. The system is comprised of a descaling unit 250,surface inspection unit 252, process control computer 254, andmultibumer scarfing unit 256. Descaling unit 250 is a high-pressurewater stream optionally containing solid particles such as iron shot,sand, etc. Surface inspection unit 252 includes a rectangular frame 258holding four detecting systems 260. Preferably, each of the detectingsystems is of the type shown in FIG. 2 and is mounted in a conduit 259having a steam free atmosphere. The spatial relationship between a slab262 and each detector 260 is such that each detector 260 inspects oneside of slab 262'by scanning in the direction normal to the motion ofthe slab. The scanning frequency is adjustable to accommodate differentslab velocities. The measured coordinates of a defect 264 shown in FIG.70 and the time interval At, of the passage of the defect under thescanning head are used by process control computer 254 to generatebumer-on signals to multiburner 256. Although not shown, multiburnerunit 256 includes a rectangular steel frame holding a number of gasburners, each burner having a separate control valve. The computer canbe either an existing general purpose process control computer or asmall specialized computing element. The surface defects information canbe presented as a dynamic visual online display, recorded forstatistical analysis, or fed online into a control system for feedbackadjustment of chemical or physical parameters of the continuous castingprocess.

Since certain changes may be made in the foregoing disclosure withoutdeparting from the scope of the invention herein involved, it isintended that all matter contained in the above detailed description anddepicted in the accompanying drawings be construed in an illustrativeand not in a limiting sense.

What is claimed is:

l. A system for remote sensing of static, geometric and dynamicproperties of a specimen being evaluated, said system comprising:

a. a source for generating a coherent beam of electromagnetic radiation;

b. scanning means operatively connected to said source;

c. detector means for sensing the presence and position of said coherentbeam as at the surface of said specimen;

d. a computer communicating with said scanning means for providingscanning signals to said source, said beam incrementally scanning thesurface of said specimen; means electrically connected to said computerfor providing output signals representative of the angular position ofsaid source; and means electrically connected to said computer forproviding output signals representative of the angular position of saiddetector means.

2. The system as claimed in claim 1 including a display electricallyconnected to said computer for presentation of the properties of thespecimen being evaluated.

3. The system as claimed in claim 2 including:

a shaker for supporting said specimen, said shaker adapted for tri-axialmovement; and

b. a driver electrically interposed between said computer and saidshaker, said driver being responsive to signals as at the output of saidcomputer, said shaker being responsive to signals as at the output ofsaid driver.

4. The system as claimed in claim 1 wherein said source is a laser.

5. The system as claimed in claim 1 wherein said detector includes anelectro-optical detector for generating signals representative of thedisplacement of a point illuminance as at the surface of said specimen.

6. A system for continuous casting of metal comprising:

a. a tundish formed with a discharge spout;

b. a mold formed with an opening at one end and a discharge opening atthe other end, said opening being in register with said spout;

c. a strand formed by said mold and discharged through said opening;

d. a plurality of guide rolls defining a curving path for carrying saidstrand;

e. at least one pair of pinch rolls, said strand passing between saidpinch rolls;

f. a plurality of spray nozzles disposed about said strand for coolingsaid strand;

g. laser means for generating a coherent beam of light toward saidstrand;

h. a receiver for sensing said illuminance as at the surface of saidstrand; 1. computer electrically connected to said receiver, the

signals as at the output of said receiver representing angularpositioning signals, the signals as at the output of said receiver beingapplied to said computer for calculation of the contour of said strand;

j. supply means for providing compressed gas;

k. conduit means operatively connected to said supply means, saidconduit means in register with said strand and in register with saidlaser means and receiver, said compressed gas being blown from saidsupply means through said conduit means toward said strand;

1. driving means operatively connected to said pinch rolls for pressingsaid pinch rolls against said strand; and

m. a control electrically connected to said computer and driving means,the signals as at the output of said control being responsive to thesignals as at the output of said computer, said driving means beingresponsive to the signals as at the output of said control, the speed ofsaid strands being regulated by said pinch rolls. 7. The system asclaimed in claim 6 including a display electrically connected to saidcomputer for presenting a record of the surface contour of said strand.

8. A system for scarfing of metal comprising:

a. means for descaling said metal;

b. a source for generating a coherent beam of electromagnetic radiation;

c. scanning means operatively connected to said source,

said coherent beam scanning the surface of the metal;

d. detector means for sensing defects in said metal;

e. computing means communicating with said detector means and scanningmeans; and

f. burner scarfing means communicating with said computing means, saidburner scarfing means being responsive to signals as at the output ofsaid computing means.

9. A system for remote sensing of static and dynamic properties of aspecimen under evaluation, said system comprising:

a source for generating a coherent beam of light;

b. first means operatively connected to said source for directing saidbeam toward said specimen, said beam defining an illuminated spot as atthe surface of said specimen, said first means generating output signalsrepresenting the angular position of said source;

c. detector means for sensing said illuminated spot as at the surface ofsaid specimen;

d. second means operatively connected to said detector means forproviding output signals representing the angular position of saiddetector means with respect to the illuminated spot as at the surface ofsaid specimen; and

e. computer means electrically communicating with said first and secondmeans, said computer means generating scanning signals to said firstsource means, said beam incrementally scanning the surface of saidspecimen;

the output signals of said first and second means Being ap plied to saidcomputer for triangulation, the distance between said source anddetector being known, said computer generating signals representative ofthe properties of said specimen.

1. A system for remote sensing of static, geometric and dynamicproperties of a specimen being evaluated, said system comprising: a. asource for generating a coherent beam of electromagnetic radiation; b.scanning means operatively connected to said source; c. detector meansfor sensing the presence and position of said coherent beam as at thesurface of said specimen; d. a computer communicating with said scanningmeans for proviDing scanning signals to said source, said beamincrementally scanning the surface of said specimen; e. meanselectrically connected to said computer for providing output signalsrepresentative of the angular position of said source; and f. meanselectrically connected to said computer for providing output signalsrepresentative of the angular position of said detector means.
 2. Thesystem as claimed in claim 1 including a display electrically connectedto said computer for presentation of the properties of the specimenbeing evaluated.
 3. The system as claimed in claim 2 including: a shakerfor supporting said specimen, said shaker adapted for tri-axialmovement; and b. a driver electrically interposed between said computerand said shaker, said driver being responsive to signals as at theoutput of said computer, said shaker being responsive to signals as atthe output of said driver.
 4. The system as claimed in claim 1 whereinsaid source is a laser.
 5. The system as claimed in claim 1 wherein saiddetector includes an electro-optical detector for generating signalsrepresentative of the displacement of a point illuminance as at thesurface of said specimen.
 6. A system for continuous casting of metalcomprising: a. a tundish formed with a discharge spout; b. a mold formedwith an opening at one end and a discharge opening at the other end,said opening being in register with said spout; c. a strand formed bysaid mold and discharged through said opening; d. a plurality of guiderolls defining a curving path for carrying said strand; e. at least onepair of pinch rolls, said strand passing between said pinch rolls; f. aplurality of spray nozzles disposed about said strand for cooling saidstrand; g. laser means for generating a coherent beam of light towardsaid strand; h. a receiver for sensing said illuminance as at thesurface of said strand; i. computer electrically connected to saidreceiver, the signals as at the output of said receiver representingangular positioning signals, the signals as at the output of saidreceiver being applied to said computer for calculation of the contourof said strand; j. supply means for providing compressed gas; k. conduitmeans operatively connected to said supply means, said conduit means inregister with said strand and in register with said laser means andreceiver, said compressed gas being blown from said supply means throughsaid conduit means toward said strand; l. driving means operativelyconnected to said pinch rolls for pressing said pinch rolls against saidstrand; and m. a control electrically connected to said computer anddriving means, the signals as at the output of said control beingresponsive to the signals as at the output of said computer, saiddriving means being responsive to the signals as at the output of saidcontrol, the speed of said strand being regulated by said pinch rolls.7. The system as claimed in claim 6 including a display electricallyconnected to said computer for presenting a record of the surfacecontour of said strand.
 8. A system for scarfing of metal comprising: a.means for descaling said metal; b. a source for generating a coherentbeam of electromagnetic radiation; c. scanning means operativelyconnected to said source, said coherent beam scanning the surface of themetal; d. detector means for sensing defects in said metal; e. computingmeans communicating with said detector means and scanning means; and f.burner scarfing means communicating with said computing means, saidburner scarfing means being responsive to signals as at the output ofsaid computing means.
 9. A system for remote sensing of static anddynamic properties of a specimen under evaluation, said systemcomprising: a. a source for generating a coherent beam of light; b.first means operatively connected to said source for directing said beamtoward said specimen, said bEam defining an illuminated spot as at thesurface of said specimen, said first means generating output signalsrepresenting the angular position of said source; c. detector means forsensing said illuminated spot as at the surface of said specimen; d.second means operatively connected to said detector means for providingoutput signals representing the angular position of said detector meanswith respect to the illuminated spot as at the surface of said specimen;and e. computer means electrically communicating with said first andsecond means, said computer means generating scanning signals to saidfirst source means, said beam incrementally scanning the surface of saidspecimen; f. the output signals of said first and second means beingapplied to said computer for triangulation, the distance between saidsource and detector being known, said computer generating signalsrepresentative of the properties of said specimen.